• Wind and Structures
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• 제14권1호
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• pp.55-70
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• 2011

This study investigates the design criteria required for wind barriers to protect vehicles running on an expressway under a high side wind. At the first stage of this study, the lateral deviations of vehicles in crosswinds were computed from the commercial software, CarSim and TruckSim, and the critical wind speeds for a car accident were then evaluated from a predefined car accident index. The critical wind speeds for driving stability were found to be 35 m/s for a small passenger car, yet 30 m/s for a truck and a bus. From the wind tunnel tests, the minimum height of a wind barrier required to reduce the wind speed by 50% was found to be 12.5% of the road width. In the case of parallel bridges, the placement of two edge wind barriers plus one wind barrier at center was recommended for a separation distance larger than 20 m (four lanes) and 10 m (six lanes) respectively, otherwise two wind barriers were recommended.

• 한국기계가공학회지
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• 제11권6호
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• pp.82-87
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• 2012

The purpose of this study is to produce a side impact beam with high tensile steel using a roll forming process. The door side impact beam plays an important roll in a car because it protects passengers from external crash. The roll forming process is a continuous bending process wherein a long metal sheet is bended as it continuously passes several rolls. The characteristic of this study is that an impact beam is produced by a continuous process using a ultra high strength steel without a hardening heat treatment. A model was determined by analysing plasticity of a cross section shape considering high strength. Design parameters of the impact beam was determined by crash-analysing the model. Workpiece products were manufactured by designing dies for roll forming and setting them up in a following process line. Results of a bending test and a FEM analysis was considered and reviewed.

• 대한기계학회논문집A
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• 제31권4호
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• pp.506-516
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• 2007

In this paper, a study on low-velocity impact response of four different sandwich panels for the hybrid bodyshell and floor structure application of the Korean low floor bus vehicle was done. Square samples of 100mm sides were subjected low-velocity impact loading using an instrumented testing machine at six energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for four different types of sandwich panels. The impact damage size and depth of the permanent indentation were measured by 3-Dimensional Scanner. Failure modes were studied by sectioning the specimens and observed under optical microscope. The impact test results show that sandwich panel with composite laminate facesheet could not observe damage mode of a permanent visible indentation after impact and has a good impact damage resistance in comparison with sandwich panel with metal aluminum facesheet.

• 설비공학논문집
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• 제7권4호
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• pp.654-666
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• 1995

R502 has been extensively used as a working fluid in transport refrigerating vehicles and low temperature refrigerating machines but is to be phased out by the end of 1995 due to ozone layer depletion problem. In this study, both theoretical cycle analysis and experiments were carried out to examine the best substitutes for R502. Theoretical results indicate that the alternatives available in the market today may replace R502 without significant changes in the system without suction line heat exchanger(SLHX). When the system contains a SLHX, however, COPs of the alternatives increase up to approximately 15~20% than those without the SLHX. But simultaneously, the discharge temperatures of the compressor also increrease significantly with the SLHX. Actual test results obtained from the experiment with a transport vehicle's refrigerator indicate the similar trend as those of the theoretical results. Especially, HFCs and their mixtures show lower discharge temperature than those of R502, which is one of the desirable features. Further research is needed to study the effect of the SLHX on the performance of the real machine as well as on the oil return for reliability of the system.

• 한국시뮬레이션학회논문지
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• 제15권1호
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• pp.43-50
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• 2006

UAV(Unmanned Air Vehicle) 시스템은 새로운 알고리즘과 소프트웨어 디자인에 바탕을 두고 빠르게 발전하고 있다. 빠르게 발전하는 현대의 UAV 시스템은 상황에 따른 효과적이고 지능적인 제어를 요구한다. 이에 본 논문에서는 UAV 시스템의 효과적이고 지능적인 제어를 위하여 이산사건 시스템인 조종사 모델과의 연동 모델링을 제안한다. 비행기 모델은 연속시간 시스템으로 표현되며, 자세한 표현력을 바탕으로 정량적이고 정확한 비행기 모델을 표현할 수 있다. 또한, 조종사 모델은 이산사건 시스템으로 표현되며, 각 사건과 시스템의 상태에 따른 정성적인 행동제어를 가능하게 한다. 본 연구는 한국항공대학교에서 개발한 이산사건 시뮬레이터인 DEJAVA(DEVS Java)와 연속시간시뮬레이터인 MATLAB 시뮬레이터 환경을 바탕으로 NASA에서 개발된 HL20 비행시뮬레이터와 지능제어시스템을 이용한 조종사 모델을 사용하여 구현되었다.

• 대한조선학회논문집
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• 제45권6호
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• pp.579-589
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• 2008

In the past few years, there are many studies and researches of the underwater vehicles which are carried out its mission using sonar sensors. MSCL(Marine System Control Lab.) at Inha University developed test-bed small ROV, ISRO. ISRO is an open-frame type and has 4 thrusters. ISRO can control 4 motions i.e surge, sway, yaw and heave with sonar sensors. ISRO is developed for inspection of ship hull, marine structure, plant of lake or river and so on. When ROV ISRO inspects something, it is necessary to control the position of ROV ISRO's for the movement and anti-collision with structures in the underwater. In this paper, we deal with the development of a small ROV and verification of the position control system via simulation and experiment using sonar sensors.

• 항공우주기술
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• 제9권1호
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• pp.125-132
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• 2010

추진제가 배출되는 동안 추진제탱크를 적정 압력으로 유지하기 위해 필요한 가압가스의 질유량 및 총소모량을 파악하는 것은 가압제어시스템의 설계 및 가압제 저장탱크의 무게를 산출하는데 있어 매우 중요하다. 특히 극저온 추진제탱크의 경우 얼리지 내부의 가압가스는 외부와의 열전달에 의해 비체적이 감소하므로 더욱 많은 추진제탱크의 압력을 유지하기 위해 더 많은 가압가스를 필요로 한다. 이에 추진제탱크 얼리지 해석을 위한 기본모델을 만들어 얼리지 내부와 탱크벽면의 온도분포, 가압가스 소모량, 얼리지 내부에서 유입된 가압가스의 에너지 분포를 예측하였다. 현재 시험을 통한 프로그램의 수정보완이 진행되었으나, 본 자료에서는 기본적인 해석모델의 설명에 중점을 두었다.

• 항공우주기술
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• 제9권1호
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• pp.106-115
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• 2010

KSLV-I 통신 시스템에 사용되는 안테나는 장착 위치가 제한되어 있어 안테나 상호간의 간섭현상이 발생하며 경항공기를 이용한 비행시험 등 각종 시험에서 이러한 간섭 현상의 영향은 더욱 증가한다. 본 논문에서는 FDTD 해석기법을 사용하여 인접한 안테나 사이의 결합량을 계산하였다. 결합량 계산을 위하여 사용된 FDTD 해석 기법에 대한 이론과 흡수 경계조건, 전압인가 방법, 결과 데이터 처리 기법을 설명하였다. 이격 거리가 5 cm이고 공진주파수가 2 GHz인 IFA 사이의 결합량은 -12.7 dB로 계산되었다. 본 논문에서 소개된 결합량 계산 방법은 KSLV-I의 시스템 성능을 분석하거나 향후 발사체의 설계에 있어서 하부시스템의 설계, 안테나 배치, 통신 링크 계산에 유용하게 사용될 수 있다.

• Structural Engineering and Mechanics
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• 제12권5호
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• pp.541-558
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• 2001

The design specifications of guard fences in Japan were reexamined and the revised specifications were implemented from April 1999. Because of the huge consumption in time and cost to test the performances of full-scale guard fences in the field, some assumptions are adopted while modifying the design specifications, and numerical analyses are necessary to confirm the impact performance and safety level of new types of steel highway guard fences. In this study, the finite element models are developed for the heavy trucks and steel highway guard fences to reenact their behaviors, and the solution approach is carried out using nonlinear dynamic analysis software of structures in three dimensions (LS-DYNA). The numerical simulation results are compared with the full-scale on-site testing results to verify the proposed analysis procedure. The collision process is simulated and it is also made possible to visualize the movement of the truck and the performances of guard fences. In addition, the energy shift of the truck kinetic energy to the truck and guard fence Internal energy, and the energy absorption of each guard fence component are studied for the development of a new design methodology of steel highway guard fences based on the energy absorption capacity.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1122-1126
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• 2017

KSLV-II 가속모터는 한국형발사체에 사용하는 단분리모터의 한 종류이며 역추진모터와 동시에 작동하여 단분리를 수행한다. 가속모터의 목표 성능에 맞는 내탄도 설계, 추진제 조성 적용, 연소관 및 경사형 노즐 설계를 수행하였다. 연소관 및 노즐의 소재로 티타늄 합금을 적용하였으며 알루미늄이 다량 함유된 추진제에 대한 내열 성능 확보를 위한 노즐 내열재 소재를 선정하였다. 지상연소시험을 수행하여 KSLV-II 요구조건에 맞는 가속모터의 연소 성능을 확보하였다.